Implement support for turning .json files into Lua modules (#308)

* Stub implementation

* Flesh out feature and add tests. Other snapshots currently failing.

* Blacklist .meta.json in JSON handler

* Write to correct property (Source) instead of Value

* Update changelog

rojo-test/src/build_test.rs

@@ -31,6 +31,7 @@ gen_build_tests! {
     init_meta_class_name,
     init_meta_properties,
     init_with_children,
+    json_as_lua,
     json_model_in_folder,
     json_model_legacy_name,
     module_in_folder,